1. Field of the Invention
This invention is concerned with a method and apparatus for use in heating shoe parts to activate adhesive on a surface thereof.
2. Prior Art
In the shoe industry, it is frequently necessary to heat a shoe part to activate adhesive thereon before adhering the part to another shoe part. For example, a shoe sole may require heating before being pressed on to a shoe to adhere the sole to the shoe. The word "shoe" where used herein is to be understood as referring to outer footwear generally whether complete or in the course of manufacture. At present this heating is usually performed by exposing the shoe part to a bank of infra-red heaters.
The infra-red heaters used at present have the disadvantage that they are color sensitive, i.e. lighter colored materials heat less rapidly than darker colored materials, so that the time for which materials are exposed to the heaters has to be varied with different colors of material. This disadvantage is caused by lack of uniformity between the degrees by which the various colors of material absorb the radiation emitted by these heaters. One example of such a heater has a bank of tubular quartz lamps having a filament operating temperature of approximately 2100.degree. C. and a radiation output which has wavelengths between 0.6 and 4.7 microns.
A further disadvantage of the present heaters is experienced when the shoe part to be heated does not have a planar surface. In this case, the distances between the shoe part and the heaters in the bank have to be made approximately equal to avoid differential heating of the shoe part and this involves adjustment of the relative heights in the bank.
It is an object of the present invention to provide a method and apparatus for use in heating shoe parts in which the above-mentioned disadvantages are avoided.